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ABSTRACT
We quantified the tritrophic effect of host plant on the susceptibility of the sweetpotato whitefly Bemisia tabaci (Genn.) to a fungal pathogen in the laboratory. Second-instar whiteflies reared on cucumber, eggplant, tomato and bean plants for six generations were exposed to conidial suspensions of Isaria fumosorosea isolate IF-1106. Our results did not detect differences in response (proportional survival or median lethal time, LT50 days) among insect populations derived from different plants that were treated with 107 conidia/ml. However, at concentrations ≤ 5×106 conidia/ml, whiteflies reared on bean and tomato died significantly more quickly (i.e. LT50 of 4–5 days) compared with cucumber and eggplant reared populations (5–7 days). Bean and tomato-reared populations were also more susceptible to mycosis (LC50 ≈ 6 × 105 conidia/ml) compared with those reared on cucumber (1.9 × 106 conidia/ml) and eggplant (1.5 × 106 conidia/ml). A separate study confirmed that this differential response of whitefly populations to I. fumosorosea was not explained by differences in deposition rate of conidia on leaf surfaces (i.e. a dosage effect). Our findings show that host plants affect the pathogenicity and virulence of a herbivore pathogen, but depend on the rate of exposure (inoculum) applied.
Acknowledgements
The authors are grateful to Huajie Qu, Xudong Zhang and Na Li for providing assistance.
Disclosure statement
No potential conflict of interest was reported by the authors.